<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        <div id="child">
            hello world
        </div>
    </div>
    <script>
        // removeChild() 让元素从DOM树，渲染树中消失
        var app = document.getElementById("app")
        var child = document.getElementById("child")
        app.removeChild(child)
    </script>
</body>
</html>